# Define here the models for your spider middleware
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/spider-middleware.html
import time

from scrapy import signals

# useful for handling different item types with a single interface
from itemadapter import is_item, ItemAdapter
from scrapy.http import HtmlResponse
from selenium import webdriver
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.common.by import By




class TutorialSpiderMiddleware:
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the spider middleware does not modify the
    # passed objects.

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_spider_input(self, response, spider):
        # Called for each response that goes through the spider
        # middleware and into the spider.

        # Should return None or raise an exception.
        return None

    def process_spider_output(self, response, result, spider):
        # Called with the results returned from the Spider, after
        # it has processed the response.

        # Must return an iterable of Request, or item objects.
        for i in result:
            yield i

    def process_spider_exception(self, response, exception, spider):
        # Called when a spider or process_spider_input() method
        # (from other spider middleware) raises an exception.

        # Should return either None or an iterable of Request or item objects.
        pass

    def process_start_requests(self, start_requests, spider):
        # Called with the start requests of the spider, and works
        # similarly to the process_spider_output() method, except
        # that it doesn’t have a response associated.

        # Must return only requests (not items).
        for r in start_requests:
            yield r

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)


class TutorialDownloaderMiddleware:
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the downloader middleware does not modify the
    # passed objects.

    def __init__(self):

        self.browser = webdriver.Chrome()
        self.browser.set_window_size(1400,800)
        self.browser.implicitly_wait(10) # 设置隐式等待时间为10秒。隐式等待是指当使用浏览器驱动查找页面元素时，
                                        # 如果元素没有立即出现，驱动会在设定的这个时间内不断尝试查找，
    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_request(self, request, spider):
        self.browser.get(request.url)
        time.sleep(2)
        target = self.browser.find_element(by=By.XPATH,value='//*[@class="nullData"]')
        for i in range(7):
            print(f"正在爬取第{i+1}页...")
            ## 每次刷新多10个li
            stop = self.browser.find_element(by=By.XPATH,value='//*[@id="__layout"]/div/div/div/section/ul/li[{}]'.format(i*10+10))
            self.browser.execute_script("arguments[0].scrollIntoView();",target)
            self.browser.execute_script("arguments[0].scrollIntoView();",stop)
            time.sleep(1) ## 一定要滑动慢一点，否则会找不到元素，就是因为如果滚动太快，页面可能来不及加载相关元素，后续操作就会出现找不到元素的错误情况。
        data = self.browser.page_source
        self.browser.close()
        return HtmlResponse(url=request.url, body=data,request=request,encoding='utf-8',status=200)

    def process_response(self, request, response, spider):
        # Called with the response returned from the downloader.

        # Must either;
        # - return a Response object
        # - return a Request object
        # - or raise IgnoreRequest
        return response

    def process_exception(self, request, exception, spider):
        # Called when a download handler or a process_request()
        # (from other downloader middleware) raises an exception.

        # Must either:
        # - return None: continue processing this exception
        # - return a Response object: stops process_exception() chain
        # - return a Request object: stops process_exception() chain
        pass

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)
